Two-piece roller retainer cage for a roller thrust bearing

ABSTRACT

A roller retainer cage for a roller thrust bearing, including a first cage half with an annular portion, a first flange extending axially from an inner peripheral edge of the annular portion and a second flange extending axially from an outer peripheral edge of the annular portion, a second cage half including an annular portion, a first flange extending axially from an inner peripheral edge of the annular portion and a second flange extending axially from an outer peripheral edge of the annular portion, wherein the first flange of the first cage half is disposed radially-outwardly of the first flange of the second cage half, the second flange of the first cage half is disposed radially-inwardly of the second flange of the second cage half, and the first cage half is comprised of a through-hardened metal.

FIELD OF THE INVENTION

The present invention relates generally to roller thrust bearings. Moreparticularly, the present invention relates to a two-piece rollerretainer cage for use in a roller thrust bearing.

BACKGROUND OF THE INVENTION

As is known in the art, roller thrust bearings typically include aroller cage including a first cage half and a second cage half thatinclude pairs of interlocking flanges that maintain the roller retainercage in a unified state. A material often used in manufacturing thistype of roller retainer cage is SAE 1010 steel, especially in high speedapplications such as air conditioning (AC) compressors. Referringadditionally to FIG. 3A, a preferred heat treatment for the cage halvesin such applications is case carburizing, which results in a case depthlayer 10 (hard zone) protecting a soft core 12 (soft zone) of thecorresponding cage half 14.

Potential issues, such as drilling wear, may arise between an end face16 of a roller 18 and the adjacent surface of the corresponding cagehalf 14. Drilling wear can be especially problematic under high speed,high temperature conditions in which inadequate lubrication exists. Asshown in FIG. 3B, drilling wear is accelerated once the roller end face16 wears through case depth layer 10 and enters soft core 12. Drillingwear is often most prevalent between the radially-outermost end faces ofthe rollers and the flanges of the corresponding retainer. It is knownto use through-hardened materials such as, but not limited to, 1074steel with standard heat treatments (SHT). However, use ofthrough-hardened materials can lead to cracking of the cage halves whenthey are crimped during the assembly process.

The present invention recognizes and addresses considerations of priorart constructions and methods.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a roller retainer cagefor a roller thrust bearing, including a first cage half with an annularportion, a first flange extending axially from an inner peripheral edgeof the annular portion and a second flange extending axially from anouter peripheral edge of the annular portion, a second cage halfincluding an annular portion, a first flange extending axially from aninner peripheral edge of the annular portion and a second flangeextending axially from an outer peripheral edge of the annular portion,wherein the first flange of the first cage half is disposedradially-outwardly of the first flange of the second cage half, thesecond flange of the first cage half is disposed radially-inwardly ofthe second flange of the second cage half, and the first cage half iscomprised of a through-hardened metal.

Another embodiment of the present invention provides a roller thrustbearing including a first cage half with an annular portion defining aplurality of roller pockets, a first flange extending axially from aninner peripheral edge of the annular portion and a second flangeextending axially from an outer peripheral edge of the annular portion,a second cage half including an annular portion defining a plurality ofroller pockets, a first flange extending axially from an innerperipheral edge of the annular portion and a second flange extendingaxially from an outer peripheral edge of the annular portion, and aplurality of roller elements, each roller element being rotatablyreceived in a corresponding roller pocket of both the first cage halfand the second cage half, wherein the second flange of the first cagehalf is disposed radially-inwardly of the second flange of the secondcage half, and the first cage half is comprised of a through-hardenedmetal.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendeddrawings, in which:

FIGS. 1A and 1B are cross-sectional views of a roller thrust bearingincluding a two-piece roller retainer cage in accordance with anembodiment of the present invention;

FIGS. 2A and 2B are cross-sectional views of a roller thrust bearingincluding a two-piece roller retainer cage in accordance with analternate embodiment of the present invention; and

FIGS. 3A and 3B are partial cross-sectional views of a two-piece rollerretainer cage in a roller thrust bearing.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention according to the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to presently preferred embodimentsof the invention, one or more examples of which are illustrated in theaccompanying drawings. Each example is provided by way of explanation,not limitation, of the invention. In fact, it will be apparent to thoseskilled in the art that modifications and variations can be made in thepresent invention without departing from the scope and spirit thereof.For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

Referring now to the figures, a roller thrust bearing 100 in accordancewith the present invention includes a roller retainer cage 110 formed bya first cage half 120 and a second cage half 140, and a plurality ofroller elements 160 rotatably received therebetween as best seen inFIGS. 1A and 1B. As shown, roller retainer cage 110 is a wrap-aroundspin cage design. First cage half 120 includes an annular portion 122defining a plurality of roller pockets 128, a first annular flange 130extending axially (parallel to longitudinal center axis 102) from itsinner peripheral edge, and a second annular flange 132 extending axiallyfrom its outer peripheral edge. Annular portion 122 of first cage half120 is substantially disc-shaped, with the inner peripheral edge and theouter peripheral edge being substantially concentric about thelongitudinal center axis 102 of roller retainer cage 110. As shown,first annular flange 130 and second annular flange 132 are preferably ofthe same height and concentric about longitudinal center axis 102 aswell.

As shown, second cage half 140 includes an annular portion 142 defininga plurality of roller pockets 148, a first annular flange 150 extendingaxially (parallel to longitudinal center axis 102) from its innerperipheral edge, and a second annular flange 152 extending axially fromits outer peripheral edge. Annular portion 142 of second cage half 140is substantially disc-shaped, with the inner peripheral edge and theouter peripheral edge being substantially concentric about longitudinalcenter axis 102 of roller retainer cage 110. As shown, unlike first cagehalf 120, first annular flange 150 and second annular flange 152 maydiffer in height although they are concentric about longitudinal centeraxis 102. Note, however, in alternate embodiments first annular flange150 and second annular flange 152 may be the same height. Note, firstcage half 120 and second cage half 140 preferably have the same materialthickness (i.e., their flanges have the same width in the radialdirection). However, in alternate embodiments, second cage half 140 maybe “thinner” than first cage half 120 as it does not have to bear thefriction with the rollers that the flanges of first cage half 120 do.

As best seen in FIG. 1B, in a preferred embodiment of roller retainercage 110, first cage half 120 is through-hardened such that no soft core12 (FIGS. 3A and 3B) is present under case depth layer 10. Rather, theentire first cage half 120 constitutes a hard zone preferably having ahardness of greater than or equal to HRC55. As such, no accelerateddrilling wear will exist as the hardness of the first cage half's firstand second flanges 130 and 132 is consistent across their entirethickness. As well, additional surface treatments may be applied to aninner surface 131 of first annular flange 130 and an inner surface 133of second annular flange 132 to further reduce friction, and thereforewear, between end faces 161 of the roller elements and the adjacentsurfaces of the corresponding cage halves. Solid lubricants such as, butnot limited to, PTFE (polytetrafluoroethylene) and MoS2 (molybdenumdisulfide) may be used, and hard coatings such as, but not limited to,DLC (diamond like carbon) and TiN (titanium nitride) may be used.

In contrast to first cage half 120, second cage half 140 is notthrough-hardened. Rather, second cage half 140 may undergo carburizingso that it retains a soft core 12 (FIGS. 3A and 3B), thereby allowingsecond cage half 140 to undergo a crimping process during assemblywithout cracking. The hardness of the soft zone of second cage half 140preferably has a value of less than HRC55. As well, alternateembodiments are possible in which second cage half 140 undergoes no heattreatment, or is alternately formed of a polymer rather than a metal. Aswell, in that first cage half 120 is preferably more resistant todrilling wear than second cage half 140, the radial width of rollerpockets 128 defined by first cage half 120 in the radial direction(i.e., along an axis that is transverse to longitude center axis 102 andbisects a corresponding roller pocket) may be selected to be less thanthe radial width of roller pockets 148 defined by second cage half 140.As such, end faces 161 of roller elements 160 will preferably makecontact with the adjacent portions of first cage half 120 rather thanthe softer second cage half 140.

Referring now to FIGS. 2A and 2B, an alternate embodiment of a rollerretainer cage 210 for use in a roller thrust bearing in accordance withthe present invention includes a first cage half 220 and a second cagehalf 240 configured to receive a plurality of roller elements 160 (FIGS.1A and 1B) rotatably therebetween. As shown, roller retainer cage 210 isa standard spin cage design. Similarly to the first embodiment, firstcage half 220 includes an annular portion 222 defining a plurality ofroller pockets 228, a first annular flange 230 extending axially(parallel to longitudinal center axis 102) from its inner peripheraledge, and a second annular flange 232 extending axially from its outerperipheral edge. Annular portion 222 of first cage half 220 issubstantially disc-shaped, with the inner peripheral edge and the outerperipheral edge being substantially concentric about the longitudinalcenter axis 102 of roller retainer cage 210. As shown, first annularflange 230 and second annular flange 232 are preferably of the sameheight and concentric about longitudinal center axis 102 as well.

Second cage half 240 includes an annular portion 242 defining aplurality of roller pockets 248, a first annular flange 250 extendingaxially (parallel to longitudinal center axis 102) from its innerperipheral edge, and a second annular flange 252 extending axially fromits outer peripheral edge. Annular portion 242 of second cage half 240is substantially disc-shaped, with the inner peripheral edge and theouter peripheral edge being substantially concentric about longitudinalcenter axis 102 of roller retainer cage 210.

Preferably, first cage half 220 is through-hardened such that no softcore 12 (FIGS. 3A and 3B) is present under case depth layer 10. Rather,the entire first cage half 220 constitutes a hard zone preferably havinga hardness of greater than or equal to HRC55. As such, no accelerateddrilling wear will exist as the hardness of the first cage half's firstand second flanges 230 and 232 is consistent across their entirethickness. Note, first cage half 220 and second cage half 240 preferablyhave the same material thickness (i.e., their flanges have the samewidth in the radial direction). However, in alternate embodiments,second cage half 240 may be “thinner” than first cage half 220 as itdoes not have to bear the friction with the rollers that the flanges offirst cage half 220 do.

In contrast to first cage half 220, second cage half 240 is notthrough-hardened. Rather, second cage half 240 may undergo carburizingso that it retains a soft core 12 (FIGS. 3A and 3B), thereby allowingsecond cage half 240 to undergo a crimping process during assemblywithout cracking. The hardness of the soft zone of second cage half 240preferably has a value of less than HRC55. As well, alternateembodiments are possible in which second cage half 240 undergoes no heattreatment, or is alternately formed of a polymer rather than a metal. Aswell, in that first cage half 220 is preferably more resistant todrilling wear than second cage half 240, the radial width of rollerpockets 228 defined by first cage half 220 in the radial direction(i.e., along an axis that is transverse to longitude center axis 102 andbisects a corresponding roller pocket) may be selected to be less thanthe radial width of roller pockets 248 defined by second cage half 240.As such, end faces 161 of roller elements 260 will preferably makecontact with the adjacent portions of first cage half 220 rather thanthe softer second cage half 240. In contrast to the first embodimentshown in FIGS. 1A and 1B, the portions of first cage half 220 that theroller element end faces 161 make contact with are the outermostsidewalls 229 and innermost sidewalls 227 of roller pockets 228, asopposed to the inner surface 133 of the first cage half's second flange132 (FIG. 1A). As such, additional surface treatments may be applied tothe outermost and innermost sidewalls 229 and 227, respectively, ofroller pockets 228 of first cage half 220 to further reduce friction,and therefore wear, between end faces 161 of the roller elements and theadjacent surfaces of roller pockets 228. Solid lubricants such as, butnot limited to, PTFE (polytetrafluoroethylene) and MoS2 (molybdenumdisulfide) may be used, and hard coatings such as, but not limited to,DLC (diamond like carbon) and TiN (titanium nitride) may be used.

While one or more preferred embodiments of the invention are describedabove, it should be appreciated by those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope and spirit thereof. It is intended thatthe present invention cover such modifications and variations as comewithin the scope and spirit of the appended claims and theirequivalents.

What is claimed is:
 1. A roller retainer cage for a roller thrustbearing, comprising: a first cage half including an annular portion, afirst flange extending axially from an inner peripheral edge of theannular portion and a second flange extending axially from an outerperipheral edge of the annular portion; and a second cage half includingan annular portion, a first flange extending axially from an innerperipheral edge of the annular portion and a second flange extendingaxially from an outer peripheral edge of the annular portion, whereinthe first flange of the first cage half is disposed radially-outwardlyof the first flange of the second cage half, the second flange of thefirst cage half is disposed radially-inwardly of the second flange ofthe second cage half, and the first cage half is comprised of athrough-hardened metal.
 2. The roller retainer cage of claim 1, whereinthe second cage half is comprised of a case carburized metal.
 3. Theroller retainer cage of claim 1, wherein the second cage half iscomprised of a polymer.
 4. The roller retainer cage of claim 1, whereinthe first cage half has an HRC hardness number of at least
 55. 5. Theroller retainer cage of claim 4, wherein the second cage half has an HRChardness number less than
 55. 6. The roller thrust bearing of claim 5,wherein a width of the first flange and the second flange of the secondcage half in the radial direction is less than a width of the firstflange and the second flange of the first cage half in the radialdirection.
 7. The roller retainer cage of claim 1, wherein an innersurface of the second flange of the first cage half includes a treatmentlayer of one of polytetrafluoroethylene, molybdenum disulfide,diamond-like carbon and titanium nitride.
 8. The roller retainer cage ofclaim 1 wherein: the annular portion of the first cage half defines aplurality of roller pockets, each roller pocket having a radial widthtaken along its longitudinal center axis that is transverse to alongitudinal center axis of the roller retainer case; the annularportion of the second cage half defines a plurality of roller pockets,each roller pocket having a radial width taken along its longitudinalcenter axis that is transverse to the longitudinal center axis of theroller retainer cage; and the radial widths of the roller pockets of thefirst cage half are less than the widths of the roller pockets of thesecond cage half.
 9. The roller retainer cage of claim 8, furthercomprising a plurality of roller elements, each roller element beingrotatably received in a corresponding roller pocket with both the firstcage half and the second cage half.
 10. A roller thrust bearing,comprising: a first cage half including an annular portion defining aplurality of roller pockets, a first flange extending axially from aninner peripheral edge of the annular portion, and a second flangeextending axially from an outer peripheral edge of the annular portion;a second cage half including an annular portion defining a plurality ofroller pockets, a first flange extending axially from an innerperipheral edge of the annular portion, and a second flange extendingaxially from an outer peripheral edge of the annular portion; and aplurality of roller elements, each roller element being rotatablyreceived in a corresponding roller pocket of both the first cage halfand the second cage half, wherein the second flange of the first cagehalf is disposed radially-inwardly of the second flange of the secondcage half, and the first cage half is comprised of a through-hardenedmetal.
 11. The roller thrust bearing of claim 10 wherein the firstflange of the first cage half is disposed radially-outwardly of thefirst flange of the second cage half.
 12. The roller thrust bearing ofclaim 11, wherein the second cage half is comprised of a case carburizedmetal.
 13. The roller thrust bearing of claim 11, wherein the secondcage half is comprised of a polymer.
 14. The roller thrust bearing ofclaim 11, wherein the first cage half has an HRC hardness number of atleast
 55. 15. The roller thrust bearing of claim 14, wherein the secondcage half has an HRC hardness number less than
 55. 16. The roller trustbearing of claim 15, wherein a width of the first flange and the secondflange of the second cage half in the radial direction is less than awidth of the first flange and the second flange of the first cage halfin the radial direction.
 17. The roller thrust bearing of claim 11,wherein an outermost sidewall of each roller pocket of the first cagehalf includes a treatment layer of one of polytetrafluoroethylene,molybdenum disulfide, diamond-like carbon and titanium nitride.